Abstract

Background

The recent detection of Rickettsia felis DNA in dogs in Australia suggests that dogs are potential mammalian reservoir hosts
for this emerging rickettsia. To date, there is no published report addressing the
seroprevalence of R. felis in dogs in Australia.

Methods

Antigens for R. felis were produced by inoculating confluent XTC-2 monolayer cell cultures with three pools
of cat flea (Ctenocephalides felis) homogenates. Infection was confirmed by real-time (qPCR), conventional or nested
PCRs targeting the ompB, gltA, 17 kDa and ompA genes. Two hundred and ninety-two dogs from Southeast Queensland and the Northern
Territory were tested for the presence of R. felis antibodies using a microimmunofluorescence (IF) test and the seroprevalence and associated
risk factors for exposure were determined using both uni- and multi-variate analyses.

Results

Rickettsia felis was successfully isolated in cell culture from all three cat-flea pools. One hundred
and forty-eight dogs (50.7%) showed seropositivity with titres ≥64 and 54 (18.5%)
with titres ≥128. At antibody titres ≥64, dogs with active ectoparasite control were
less likely to be seropositive to R. felis (OR: 2.60; 95% CI: 1.20 - 5.56).

Conclusions

This first reported isolation of R. felis in cell culture in Australia allowed for the production of antigen for serological
testing of dogs. Results of this serological testing reflects the ubiquitous exposure
of dogs to R. felis and advocate for owner vigilance with regards to ectoparasite control on domestic
pets.